package com.leetcode.linkedList;

import com.leetcode.basic.ListNode;

/**
 * @author Dennis Li
 * @date 2020/6/11 21:10
 */
public class MergeLinkedLists_21 {
    public ListNode mergeTwoListsTraverse(ListNode l1, ListNode l2) {
        if (l1 == null) return l2;
        if (l2 == null) return l1;
        if (l1.val < l2.val) {
            l1.next = mergeTwoListsTraverse(l1.next, l2);
            return l1;
        } else {
            l2.next = mergeTwoListsTraverse(l1, l2.next);
            return l2;
        }
    }

    public ListNode mergeTwoLists(ListNode l1, ListNode l2) {
        if (l1 == null) return l2;
        if (l2 == null) return l1;

        if (l1.val < l2.val) {
            l1.next = mergeTwoLists(l1.next, l2);
        } else {
            l2.next = mergeTwoLists(l1, l2.next);
        }

        return l1.val < l2.val ? l1 : l2;
    }

}
